In a new audio recording, the son of Al-Qaeda founder Osama bin Laden reportedly urges militants to travel to Syria and unite in a battle to ultimately liberate Palestine.

"There is no longer an excuse for those who insist on division and disputes now that the whole world has mobilized against Muslims," Hamza, 23, says in a message posted online on May 9.

Bin Laden was believed to have been grooming Hamza to take over as Al-Qaeda's leader before he was killed by U.S. forces in 2011.

Hamza bin Laden's message comes after Al-Qaeda leader Ayman al-Zawahri urged militants in Syria to unite, through he continued to reject the rival Islamic State group.

"The matter of unity today is one of life and death," Zawahri said in an audio message posted on May 7. "Either you unite to live as Muslims with dignity, or you bicker and separate and so are eaten one by one."

Al-Qaeda's Syria affiliate, Al-Nusra Front, is a rival of IS, which is an Al-Qaeda offshoot whose leader, Abu Bakr al-Baghdadi, in 2014 declared an Islamic caliphate across territory seized in Iraq and Syria.